Non-imaging facet based optics
A high efficiency and compact optical device comprising two or more active and resonating optical facet surfaces defined by a three-dimensional representation and configured to provide a three-dimensional device. A focal region, remote from the optical surfaces and non-contiguous therewith, is defined by two or more active optical resonant surfaces, at least one of which is self-resonant. The optical surfaces in general do not have a continuous second derivative and are defined by a piecewise continuous surface function providing radially directed facets. The optical device comprises a transparent dielectric body with its optical surfaces being formed on the surfaces of said transparent dielectric body. A light transducer may be located at a focal region to provide an energy conversion. A light source having a physical extension in space, such as an LED, may be located at the focal region to provide collimation. In some embodiments the active surfaces may be chosen to transform incident radiation into a predetermined shape and having a predetermined spatial power distribution.
1. An optical device, defined in a polar coordinate system, having its optical axis coincident with said polar coordinate system's z-axis axis, whereby said optical device transforms a first distribution of light, propagating along said optical axis, into a second distribution of light, propagating towards a focal region, comprising:
a. a first optically active surface that is radially symmetric about the optical axis and providing continuous first and second partial derivatives of its surface function at all surface points and in all directions that are tangent to said first optically active surface at each said surface point, except at the location of said optical axis.
b. a second optically active surface, displaced along said optical axis apart from said first optically active surface, and providing a plurality of radially directed facets each having two active and symmetric local surfaces arranged at an inclined Geometric Facet Angle to each other and extending radially away from the vicinity of the optical axis and having continuous first and second partial derivatives of its surface function in the polar angle direction, except for discrete polar angles of said polar coordinate system where said first partial derivative in the polar angle direction is discontinuous,
c. said second optically active surface providing continuous first and second partial derivatives of its surface function in the radial direction of said polar coordinate system of said optical device,
d. each of said facets having said Geometric Facet Angle that continuously varies as a function of the radial coordinate of said optical device,
f. a focal region which is symmetrically located about said optical axis, and
g. a transparent dielectric medium having its boundaries defined predominately by said first optically active surface and said second optically active surface and having a refractive index that is higher than the refractive index of a surrounding medium,
whereby said first distribution of light is transformed jointly by said first optically active surface and said second optically active surface to said focal region by a series of light redirections comprising at least: a refraction through said first surface, two total internal reflections on said two active and symmetric local surfaces of said radially directed facets, thereby allowing said first distribution of light to be transformed into said second distribution of light at said focal region.
2. The method of claim 1 wherein the direction of the light is reversed to transform a second distribution of light from said focal region to a first distribution of light along the optical axis in order to provide a collimator.
3. The method of claim 1 further comprising a sub-reflector located on or in close proximity to said first optically active surface, wherein the sub-reflector is a mirror.
4. The method of claim 1 further comprising a sub-reflector located on or in close proximity to said first optically active surface, wherein the sub-reflector is a diffuser.
5. The method of claim 1 wherein a plurality of facet geometries is utilized to control the overall second distribution of light.
6. The optical device of claim 1 further comprising a hole in said solid, optically transmissive material to allow for external connection to an energy conversion device located at said focal region within said optically transmissive material.
7. The optical device of claim 1 wherein said transparent dielectric medium further comprises one or more gas filled or vacuum filled cavities to provide light-loss protection for total internal reflection from dirt from the surrounding environment.
8. The optical device of claim 1 further comprising a receiving device located at said focal region, thereby providing a concentrator.
9. The optical device according to claim 1 , wherein said Geometric Facet Angle monotonically decreases in extent from approximately a 90 degree angle to approximately a 10 degree variation below 90 degree angle.
10. The optical device of claim 1 wherein a portion of one or more of said optically active surfaces redirects light by diffraction.
11. The optical device of claim 1 wherein a portion of one or more of said optically active surfaces redirects light by mirror reflections.
12. The optical device of claim 1 wherein a portion of one or more of said optically active surfaces redirects light by total internal reflection.
13. The optical device of claim 1 wherein said focal region is located internal to said optical device.
14. The optical device of claim 1 wherein said focal region is located external to said optical device.
15. The optical device of claim 1 wherein a plurality of said optical devices are formed into an array.